Teaching socio-scientific issues (SSI) fosters students' ethical reasoning, yet many educators struggle with integrating these topics into science classrooms. This exploratory mixed-methods study investigates how ethical reflection influences adolescents' attitudes toward animal experimentation and their ethical orientations. The study involved 72 students, who were assigned to one of three groups: an experimental group (animal ethics workshop), a comparison group (environmental issues workshop), or a control group. Pre- and post-surveys measured shifts in animal ethical orientations. We also analysed the experimental group's decisions on animal ethics issues using qualitative content analysis. The findings show a high level of acceptance of animal experimentation, shaped by contextual factors such as suffering of animals and research purpose. Utilitarian reasoning increased in the experimental group. This suggests that ethical reflection does not always lead to greater consideration for animals. This study highlights the challenges of SSI education, particularly the risk of instructional bias and the need for balanced ethical discussions in science classrooms. Future research should explore long-term effects and methods to minimise teaching bias.